Automatic sample changer for x-ray fluorescence spectrometer

ABSTRACT

X-ray fluorescence spectrometer apparatus for automatically analyzing a predetermined number of sample discs. A turntable mounts a plurality of sample holders, each of which can receive a plurality of discs. Prior to analysis, the discs are loaded in sample storage means connected to sample injector means by special gating means. The sample injector means sequentially injects discs into the sample holders as the turntable revolves. Drive means for rotating the turntable in predetermined steps is disclosed.

United States Patent New York, N.Y.

AUTOMATIC SAMPLE CHANGER FOR X-RAY FLUORESCENCE SPECTROMETER 6 Claims, 9 Drawing Figs.

US. Cl

Int. Cl

Field of Search ..G0ln 23/22 [56] References Cited UNITED STATES PATENTS 2,500,492 3/1950 Henriques, Jr. 250/106 X 2,843,753 7/1958 Meeder 250/l06 3,263,078 7/l966 Thackara et al. 250/515 3,4l5,987 12/1968 Sahores 250/515 Primary ExaminerWilliam F. Lindquist An0rney.r Blucher S. Tharp and Robert E. Lee, Jr.

predetermined steps is disclosed.

.1 i z 23 J i as I as PATENTEU rmvso 19H SHEET 1 BF 3 SAMPLE STORAGE MEANS GATING MEANS l4 SAMPLE INJ.

MEANS 12 X RAY SOURC E l6 SAMPLE HOLDERS TURNTABLE u j DRIVE MEANS l5 37 Fig. 2

INVENTORS Carl A. Youngmon Glenn D. Roe

RM MN. L,

Attorney AUTOMATIC SAMPLE CHANGER FOR X-RAY FLUORESCENCE SPECTROMETER BACKGROUND OF THE INVENTION The invention generally relates to material or article handling and particularly concerns an automatic sample changer for an X-ray spectrometer.

X ray fluorescence analysis is a nondestructive physical method used for chemical analysis of solids and liquids. The specimen is irradiated by an intense X-ray beam which causes the elements in the specimen material to emit, i.e. fluoresce, characteristic X-ray line spectra. The lines of the spectra are diffracted at various angles which vary in a regular manner with atomic number. The elements may be identified by the wavelengths of their spectral lines and their concentrations may be determined from the intensities of the lines. Counter tubes and associated electronic circuits are used to measure X-ray intensities.

Complete equipment for conducting X-ray analysis is available from several companies; however, even in sophisticated devices the specimen to be analyzed are moved manually. A turret mechanism generally allows four or six samples to be loaded at one time; however, an operator must be permanently present to operate the turret mechanism and also to reload the spectrometer after each group of samples is analyzed. When a large number of samples is to be analyzed, such manual manipulations are time consuming, troublesome, costly, and highly undesirable.

SUMMARY OF THE INVENTION The invention relates to Xray fluorescence spectrometer apparatus capable of automatically positioning 60 or more specimen for analysis at a single loading. A plurality of sample holders, each of which is adapted to receive a plurality of sample discs, is mounted at spaced intervals on the periphery of a turntable. Sample injector means is positioned above the turntable for sequentially injecting sample discs into the sample holders. The sample injector means is pneumatically actuated and includes upper and lower axially arranged cylinders with a common piston rod. Sample storage means is connected to the sample injector means for holding the sample discs prior to analysis. Gating means actuated by the sample injector means controls the release of sample discs form the sample storage means. An inclined ramp leads from the sample storage means to the sample injector means so that sample discs released by the gating means slide down the ramp into the lower cylinder. Drive means rotates the turntable so that the sample holders are progressively aligned beneath the sample injector means. The drive means includes a reversible electric motor and a clutch mechanism for transmitting unidirectional circular motion to the turntable.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic representation showing the basic components of the invention.

FIG. 2 is a drawing of the sample changer with a cutaway view showing the sample injector means in its down position.

FIG. 3 is a sectional view of the sample changer showing the sample injector means in its up position.

FIG. 4 is a fragmentary drawing showing the turntable and sample holders.

FIG. 5a and 5b are views showing a sample disc with FIG. 5b being taken along line AA of FIG. 5a.

FIGS. 60 and 6b illustrate the construction of an alternate sample disc with FIG. 6b being taken along line 8-8 of FIG. 6a.

FIG. 7 is a schematic drawing showing the preferred drive means for the turntable.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S) Referring to FIG. 1, a plurality of sample holders 10 are positioned on the periphery of turntable 11. Each sample holder 10 is capable of containing a plurality of sample discs of the type shown in FIGS. 5a and 5b or FIGS. 60 and 6b. The sample discs are injected into sample holders 10 by sample injector means 12. Sample storage storage means 13 is a preanalysis storage reservoir in which the sample discs to be analyzed are initially loaded. Gating means 14 is actuated each cycle so that a sample disc is transferred from sample storage means 13 to sample injector means 12. Meantime,

drive means I5 rotates turntable 11 one step each cycle so that the sample discs are sequentially distributed by sample injector means 12 among sample holders I0. Each sample disc is analyzed as it is rotated in front of X-ray source 16. After a first sample disc in each sample holder 10 has been analyzed, the above sequence of operations is repeated and a second sample disc is introduced into each holder. This process is continued until each of the several sample holders contain a full stack of discs.

Referring now to FIGS. 2 and 3, sample storage means 17 is vertically mounted on support means 18 and is comprised of slotted storage tube or magazine 19 and assembly cover 20. Gating arm 21 is movably disposed beneath sample storage means 17 so that aperture 22 (FIG. 3) can be vertically aligned, or misaligned, with respect to the outlet of storage tube 19. At its opposite end, gating arm 21 has aperture 23 adapted to receive piston rod 24. The lower part of aperture 23 is tapered (FIG. 3) so that engagement with rod cone 25 causes gating arm 21 to move laterally, aligning aperture 22 along the axis of storage tube 19. At the same time, clamping ring 26 is compressed, closing off the outlet of storage tube 19. When gating arm 21 and rod cone 25 disengage on the downstroke, spring member 27 (FIG. 3) moves gating arm 21 back to its original position so that aperture 22 is out of alignment with the outlet ofstorage tube 19.

As already noted, piston rod 24 passes through aperture 23 of gating arm 21. At its upper end, piston rod 24 connects to actuator piston 28 and, at its bottom end, to injector piston 29. As actuator piston 28 moves up and down in upper cylinder 30, injector piston 29 is driven in a corresponding manner in lower cylinder 31. Upper and lower cylinders 30 and 3I are divided from each other by cylinder seal 32 which acts as ajournal bearing about piston rod 24.

Actuator piston 28 is driven by pneumatic action; compressed air is alternatively introduced through ports 33 and 34 while the other port is vented to the atmosphere. To force actuator piston 28 downward, compressed air is admitted through port 33, while air trapped between actuator piston 28 and cylinder seal 32 is allowed to escape via port 34. The cycle is completed by reversing the air flow so that compressed air is admitted through port 34, driving actuator piston 28 upward, while air trapped above it is allowed to escape via port 33. At the top of the upstroke, actuator piston 28 engages plunger 35 which actuates a switch (not shown) designed to allow another cycle. Failure to actuate this switch initiates a countdown procedure which terminates the analysis.

Inclined ramp 36 is mounted on support base 18 beneath sample storage means 17 so as to form slide means leading to lower cylinder 31. On the upstroke (FIG. 3), injector piston 29 raises above the juncture with ramp 36 and, on the downstroke (FIG. 2), it traverses ramp 36, penetrates flexible members 37, and terminates at the bottom of lower cylinder 31. Positioned immediately below lower cylinder 31 is sample holder 38 mounted on turntable 39. As seen in FIG. 4, a plurality of identical sample holders such as 37 are mounted at regular intervals on the periphery of turntable 39. Rotation of turntable 39 causes sample holders 38 to be sequentially aligned beneath the bore of lower cylinder 31, FIGS. 2 and 3, on progressive downstrokes of injector piston 29.

Drive means for turntable 39 is shown in FIG. 7. Reversible electric motor 40 drives motor shaft 41 which in turn connects to clutch mechanism 42. Motor shaft 41 connects to and rotates upper rotator 43 and adapter shaft 44. Pin 45 on the top of upper rotator 43 causes actuator arm 46 to pivot about arm pin 47 and actuate switch means 48. Adapter shaft 44 supports and acts as a bearing for lower rotator cover 49 which encloses lower rotator plate 50. Pawl 51 is attached to upper rotator 43 by pins 52 and 53 so that it is slidably mounted on the top surface of lower rotator cover 50. Pin 54 is integral with lower rotator plate 50 and extends upward through an aperture in lower rotator cover 49 so that it is engageable by pawl 51. Pawl spring 55 fits between pawl 51 and adapter shaft 44 and holds pawl 51 in desired relation to pin 54. Lower rotator plate 50 connects to the turns output shaft 56 in a clockwise direction; counterclockwise movement of plate 50 and shaft 56 is prevented by rachet means 57. Spring means (not shown) holds rachet pawl 58 against the detents in rachet 59. Output shaft 56 connects to turntable shaft 60 via gear means 61.

ln operation, a preselected number of sample discs are loaded into storage tube 19, FIGS. 2 and 3, with injector piston 29 in its up position. A cylindrical weight (not shown) is placed on top of the samples and assembly cover 20 is replaced. In this position, aperture 22 of gating am 21 is aligned with the outlet from storage tube 19; however, clamping ring 26 is closed, holding the discs in place. Compressed air is introduced into upper cylinder 30 via port 33 driving actuator piston 28 downward. This causes piston rod 24 to move injector piston 29 in lower cylinder 31 so that rod cone 25 releases clamping ring 26 and allows gating arm 21 to retract. As aperture 22 moves out of axial alignment with storage tube 19, the bottommost disc is released by clamping ring 26 and falls through aperture 22 onto the protruding lip of gating arm 21. Compressed air is snow introduced into upper cylinder 31 via port 34 driving actuator piston 28 upward so that rod cone 25 again engages gating arm 21. This releases the first sample disc which slides down ramp 36 into the environs of lower cylinder 31 where it is retained by flexible members 37. The remaining sample discs are held in place in storage tube 19 by retaining ring 26 which closes on the upstroke.

When injector piston 29 next starts its downstroke, rod cone 25 disengages from gating arm 21; this causes gating arm 21 to be biased by spring 27 so that aperture 22 moves into alignment with the outlet storage tube 19. At the same time, retaining ring 26 reopens and allows the second sample disc to drop onto lip of gating arm 21. As injector piston 29 completes its downstroke, it engages the first sample disc and drives it into sample holder 38 which is axially aligned with the bore of lower cylinder 31. The flow of compressed air is now automatically reversed so that actuator piston 28 is driven upward so that the second disc is released into lower cylinder 31. When the upstroke is completed, plunger 35 is actuated, allowing continued operation.

.The aforesaid sequence of steps is automatically repeated for an additional cycle or cycles so long as there are sample discs loaded in storage tube 19. Turntable 39 rotates so that the discs are sequentially injected into each of sample holders 38. After all the sample holders have received one disc, a second layer of discs is distributed, etc. (The sample holders preferred by applicants are designed to hold l pellets each.) However, as the last sample disc is being injected into a sample holder, the weight previously referred to drops into aperture 22 of gating arm 21. As a result, when rod cone 25 engages gating arm 21 on the following upstroke, lateral movement of gating arm 21 is prevented, stopping pistons 28 and 29 short of their normal up positions. Failure of actuator piston 28 to contact plunger 35 triggers a relay shutting off the apparatus after the last sample disc has been analyzed. (Applicants load five sample holders in advance of analysis so that turntable 39 must turn four positions before it can shutoff.)

The drive means for turntable 39, FIG. 7, operated to sequentially move sample holders 38 into position to receive sample discs as follows: Motor 40 turns shaft 41 which in turn rotates upper rotator 43 and adapter shaft 44 in a clockwise direction. Upper rotator 43 drives pawl 51 by means of pins 52 and 53 which, in turn, rotates lower rotator cover 49 and lower rotator plate 50. Output shaft 56 drives turntable shaft 60 such that turntable 39 is rotated a predetermined number of degrees, positioning the sample holder next in line beneath lower cylinder 31 (FIGS. 2 and 3). When pin 45 completes a revolution, it engages actuator arm 46, actuating switching means 48 which causes motor 40 to reverse. Upper rotator 43 is then driven in a counterclockwise direction so that pawl 51 makes a completecircle about adapter shaft 44 while lower rotator cover 49 and plate 50 are held by rachet means 57 so that their counterclockwise rotation is prevented. As pawl 51 passes between shaft 44 and pin 54, spring 55 forces it into the position shown in FIG. 7. At completion of the sample analysis, pin 45 engages actuator arm 46 a second time so that switching means 48 again reverses motor 40, rotating shaft 41 in a clockwise direction so that the entire cycle can be repeated, if desired. After the last sample pallet has been loaded, turntable 39 is rotated until each of the loaded discs has been analyzed; then the drive means also turns off.

Sample discs which applicants have designed for use in their sample changer are shown in FIGS. 5a and 5b and FIGS. 60 and 6b.

Referring first to FIGS. 5a and 5b, disc 62 is comprised of plate 63 which contains sample material or powder 64 in binder 65. Disc 62 is prepared by filling plate 63 with binder 65, e.g. paraffin, and then embedding sample material 64 by applied pressure. Disc 62 is finished by applying a coating of clear plastic (not shown) to its exposed surface.

Referring not to FIGS. 6a and 6b, disc 66 is comprised of plastic plate 67 having double-sided adhesive tape 68 attached thereto. Sample powder 69 is then sprinkled on top of tape 68 so that it adheres to the upper surface. A coating of clear plastic (not shown) may be applied to the exposed surface.

What is claimed is:

1. Automatic sample changing apparatus for automatically positioning a predetermined number of sample discs for analysis in an X-ray fluorescence spectrometer comprising a. a plurality of sample holders, each of which is adapted to receive and store a plurality of sample discs, mounted at spaced intervals on the periphery of turntable,

b. pneumatically actuated sample injector means positioned above the turntable for sequentially injecting sample discs into the sample holders,

c. sample storage means connected to the sample injector means for holding the sample discs prior to analysis, and

d. drive means for rotating the turntable so that the sample holders are progressively aligned beneath the sample injector means.

2. Apparatus according to claim 1 where said sample injector means includes upper and lower axially arranged cylinders with a common piston rod.

3. Apparatus according to claim 1 where gating means actuated by said sample injector means controls the release of sample discs from said sample storage means.

4. Automatic sample changing apparatus for automatically positioning a predetermined number of sample discs for analysis in an X-ray fluorescence spectrometer comprising a. a plurality of sample holders, each of which is adapted to receive and store a plurality of sample discs, mounted at spaced intervals on the periphery of a turntable,

b. pneumatically actuated sample injector means mounted above the turntable for sequentially injecting sample discs into the sample holders, said injector means including upper and lower axially arranged cylinders with a common piston rod,

c. sample storage means connected to the sample injector means for holding the sample discs prior to analysis,

d. gating means actuated by the sample injector means controlling the release of sample discs from the sample storage means, and

c. drive means for rotating the turntable so that the sample holders are progressively aligned beneath the sample inector means.

5. Apparatus according to claim 4 where an inclined ramp leading from the sample storage means to the sample injector means allows sample discs released by the gating means to slide beneath lower cylinder.

6. Apparatus according to claim 4 where said drive means includes a reversible electric motor and a clutch mechanism for transmitting undirectional circular motion to the turntable.

t t i 1! i 

1. Automatic sample changing apparatus for automatically positioning a predetermined number of sample discs for analysis in an X-ray fluorescence spectrometer comprising a. a plurality of sample holders, each of which is adapted to receive and store a plurality of sample discs, mounted at spaced intervals on the periphery of a turntable, b. pneumatically actuated sample injector means positioned above the turntable for sequentially injecting sample discs into the sample holders, c. sample storage means connected to the sample injector means for holding the sample discs prior to analysis, and d. drive means for roTating the turntable so that the sample holders are progressively aligned beneath the sample injector means.
 2. Apparatus according to claim 1 where said sample injector means includes upper and lower axially arranged cylinders with a common piston rod.
 3. Apparatus according to claim 1 where gating means actuated by said sample injector means controls the release of sample discs from said sample storage means.
 4. Automatic sample changing apparatus for automatically positioning a predetermined number of sample discs for analysis in an X-ray fluorescence spectrometer comprising a. a plurality of sample holders, each of which is adapted to receive and store a plurality of sample discs, mounted at spaced intervals on the periphery of a turntable, b. pneumatically actuated sample injector means mounted above the turntable for sequentially injecting sample discs into the sample holders, said injector means including upper and lower axially arranged cylinders with a common piston rod, c. sample storage means connected to the sample injector means for holding the sample discs prior to analysis, d. gating means actuated by the sample injector means controlling the release of sample discs from the sample storage means, and e. drive means for rotating the turntable so that the sample holders are progressively aligned beneath the sample injector means.
 5. Apparatus according to claim 4 where an inclined ramp leading from the sample storage means to the sample injector means allows sample discs released by the gating means to slide beneath lower cylinder.
 6. Apparatus according to claim 4 where said drive means includes a reversible electric motor and a clutch mechanism for transmitting undirectional circular motion to the turntable. 